package com.sywb.chuangyebao.utils;

import org.bining.footstone.utils.Base64Utils;

import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Random;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

/**
 * 微信AES加解密
 */
public class AESUtils {

    private static String SECRETKEY = "1x7I6naLY9djofbgpqPRTNWcPMzzQAhF52L0wjjSrXE=";//K3h0rAIKvOSjUvNcQokT7aZooNncPDVTvSEysixt7v0GXnHFoMEJ9cg9qS8GwEmCfYIvHAvb2o6prOqIvJzqbPqkllrBlghE8lccEIIBBbI=
    private static String RANDOM = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
    private static Charset CHARSET = Charset.forName("utf-8");
    private static int BLOCK_SIZE = 32;
    private static String WAY = "AES/CBC/NoPadding";
    private static String AES = "AES";

    // 随机生成16位字符串
    public static String getRandomStr() {
        Random random = new Random();
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < 16; i++) {
            int number = random.nextInt(RANDOM.length());
            sb.append(RANDOM.charAt(number));
        }
        return sb.toString();
    }

    // 生成4个字节的网络字节序
    public static byte[] getNetworkBytesOrder(int sourceNumber) {
        byte[] orderBytes = new byte[4];
        orderBytes[3] = (byte) (sourceNumber & 0xFF);
        orderBytes[2] = (byte) (sourceNumber >> 8 & 0xFF);
        orderBytes[1] = (byte) (sourceNumber >> 16 & 0xFF);
        orderBytes[0] = (byte) (sourceNumber >> 24 & 0xFF);
        return orderBytes;
    }

    // 还原4个字节的网络字节序
    public static int recoverNetworkBytesOrder(byte[] orderBytes) {
        int sourceNumber = 0;
        for (int i = 0; i < 4; i++) {
            sourceNumber <<= 8;
            sourceNumber |= orderBytes[i] & 0xff;
        }
        return sourceNumber;
    }

    public static byte[] getKey() {
        byte[] baseKey = Base64Utils.decode(SECRETKEY);
        byte[] keyByte = new byte[32];
        System.arraycopy(baseKey, 0, keyByte, 0, 32);
        return keyByte;
    }

    /**
     * 对明文进行加密.
     *
     * @param data 需要加密的明文
     * @return 加密后base64编码的字符串
     */
    public static String encrypt(String data) {
        ArrayList<Byte> byteContainer = new ArrayList<Byte>();

        byte[] randomStrBytes = getRandomStr().getBytes(CHARSET);
        byte[] textBytes = data.getBytes(CHARSET);
        byte[] networkBytesOrder = getNetworkBytesOrder(textBytes.length);

        for (byte b : randomStrBytes) {
            byteContainer.add(b);
        }

        for (byte b : networkBytesOrder) {
            byteContainer.add(b);
        }

        for (byte b : textBytes) {
            byteContainer.add(b);
        }

        // ... + pad: 使用自定义的填充方式对明文进行补位填充
        byte[] padBytes = encode(byteContainer.size());

        for (byte b : padBytes) {
            byteContainer.add(b);
        }

        // 获得最终的字节流, 未加密
        byte[] unencrypted = new byte[byteContainer.size()];
        for (int i = 0; i < byteContainer.size(); i++) {
            unencrypted[i] = byteContainer.get(i);
        }

        try {
            // 设置加密模式为AES的CBC模式
            Cipher cipher = Cipher.getInstance(WAY);
            SecretKeySpec keySpec = new SecretKeySpec(getKey(), AES);
            IvParameterSpec iv = new IvParameterSpec(getKey(), 0, 16);
            cipher.init(Cipher.ENCRYPT_MODE, keySpec, iv);

            // 加密
            byte[] encrypted = cipher.doFinal(unencrypted);

            // 使用BASE64对加密后的字符串进行编码
            String base64Encrypted = Base64Utils.encode(encrypted);

            return base64Encrypted;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 对密文进行解密.
     *
     * @param data 需要解密的密文
     * @return 解密得到的明文
     */
    public static String decrypt(String data) {
        byte[] original = null;
        try {
            // 设置解密模式为AES的CBC模式
            Cipher cipher = Cipher.getInstance(WAY);
            SecretKeySpec key_spec = new SecretKeySpec(getKey(), AES);
            IvParameterSpec iv = new IvParameterSpec(Arrays.copyOfRange(getKey(), 0, 16));
            cipher.init(Cipher.DECRYPT_MODE, key_spec, iv);

            // 使用BASE64对密文进行解码
            byte[] encrypted = Base64Utils.decode(data);

            // 解密
            original = cipher.doFinal(encrypted);
        } catch (Exception e) {
            e.printStackTrace();
        }

        String xmlContent = null;
        try {
            // 去除补位字符
            byte[] bytes = decode(original);
            // 分离16位随机字符串,网络字节序和AppId
            byte[] networkOrder = Arrays.copyOfRange(bytes, 16, 20);
            int xmlLength = recoverNetworkBytesOrder(networkOrder);
            // xmlContent = new String(Arrays.copyOfRange(bytes, 20, bytes.length), CHARSET);
            xmlContent = new String(Arrays.copyOfRange(bytes, 20, 20 + xmlLength), CHARSET);
        } catch (Exception e) {
            e.printStackTrace();
        }

        return xmlContent;
    }

    /**
     * 获得对明文进行补位填充的字节.
     *
     * @param count 需要进行填充补位操作的明文字节个数
     * @return 补齐用的字节数组
     */
    static byte[] encode(int count) {
        // 计算需要填充的位数
        int amountToPad = BLOCK_SIZE - (count % BLOCK_SIZE);
        if (amountToPad == 0) {
            amountToPad = BLOCK_SIZE;
        }
        // 获得补位所用的字符
        char padChr = chr(amountToPad);
        String tmp = new String();
        for (int index = 0; index < amountToPad; index++) {
            tmp += padChr;
        }
        return tmp.getBytes(CHARSET);
    }

    /**
     * 删除解密后明文的补位字符
     *
     * @param decrypted 解密后的明文
     * @return 删除补位字符后的明文
     */
    static byte[] decode(byte[] decrypted) {
        int pad = (int) decrypted[decrypted.length - 1];
        if (pad < 1 || pad > 32) {
            pad = 0;
        }
        return Arrays.copyOfRange(decrypted, 0, decrypted.length - pad);
    }

    /**
     * 将数字转化成ASCII码对应的字符，用于对明文进行补码
     *
     * @param a 需要转化的数字
     * @return 转化得到的字符
     */
    static char chr(int a) {
        byte target = (byte) (a & 0xFF);
        return (char) target;
    }

}